The present invention relates to a positive photosensitive composition used in the production process of semiconductor devices, for example, IC, in the production of circuit substrates for liquid crystals or thermal heads, or in other photofabrication processes. More specifically, the present invention pertains to a positive photosensitive composition suitable for use a far ultraviolet ray of not more than 250 nm as a light source for exposure.
A chemically amplified positive resist composition is a pattern formation material in which an acid is generated in the exposed area upon irradiation of radiation, for example, a far ultraviolet ray, and solubility in a developer between the exposed area and unexposed area is differentiated by a reaction using the acid as a catalyst, whereby a pattern is formed on a substrate.
Since the composition is mainly composed of a resin having as a basic skeleton, poly(hydroxystyrene) that has a small absorption in a region of 248 nm, a good pattern with high sensitivity and high resolution is formed, when a KrF excimer laser is used as a light source for exposure. Thus, the composition is superior to a conventional resist composition using a naphthoquinonediazide/novolac resin.
When a light source having a shorter wavelength, e.g., an ArF excimer laser (193 nm) is used for exposure, on the other hand, since an aromatic group-containing compound essentially has a large absorption in a region of 193 nm, the above-described chemically amplified composition is still insufficient.
The use of poly(meth)acrylate as a polymer having a small absorption in a wavelength range of 193 nm is described in J. Vac. Sci. Technol., B9, 3357(1991). The polymer has, however, a problem in that resistance to dry etching ordinarily performed in a semiconductor production process is low in comparison with conventional phenolic resins having an aromatic group.
A mixed acid generator of a specific sulfonium salt (an anion having from 1 to 15 carbon atoms) and a triarylsulfonium salt is described in JP-A-2000-292917 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d), a mixed acid generator of a triphenylsulfonium salt of a perfluoroalkanesulfonic acid having from 4 to 8 carbon atoms and a 2-alkyl-2-adamantyl (meth)acrylate is described in JP-A-2000-275845, and a mixed acid generator of a specific sulfonium salt (an anion having from 1 to 8 carbon atoms) and a triphenylsulfonium salt or iodonium salt of a perfluoroalkanesulfonic acid having from 4 to 8 carbon atoms is described in EP 1041442A.
As increasing fine processing of semiconductor device, it has been desired more and more for a photoresist to have a low pitch dependency, specifically, to be capable of forming good patterns in both a dense portion and a sparse portion, in addition to improved sensitivity and resolution in lithography using a chemically amplified resist for far ultraviolet ray exposure. However, means for improving the pitch dependency of chemically amplified resist for far ultraviolet ray exposure has been scarcely disclosed. The addition of an orthoester compound to a chemically amplified resist composition for a KrF excimer laser for improving the pitch dependency is just described in JP-A-11-160876.
A resist composition containing a resin based on hydroxystyrene having a high hydrophilicity and a mixture of acid generators generating acids having acidities different from each other is described in JP-A-2000-241965. However, since the hydroxystyrene structure has an excessively high absorption to light of not more than 220 nm, e.g., an ArF excimer laser (193 nm), a problem of the formation of a pattern profile called taper arises, when such a resist composition is used for the formation of resist pattern.
Therefore, an object of the present invention is to provide a positive photosensitive composition that is excellent in sensitivity and resolution.
Another object of the present invention is to provide a positive photosensitive composition that exhibits a low pitch dependency as well as excellent sensitivity and resolution.
Other objects of the present invention will become apparent from the following description.
As a result of the intensive investigations, it has been found that the above-described objects can be accomplished by using compounds generating acids having specific structures in combination to complete the present invention.
Specifically, the present invention includes the following positive photosensitive compositions:
1. A positive photosensitive composition comprising (A1) a compound that generates an alkanesulfonic acid in which the xcex1-position is substituted with a fluorine atom upon irradiation of an actinic ray or radiation, (A2) an onium salt of an alkanesulfonic acid in which the xcex1-position is not substituted with a fluorine atom, and (B) a resin that has a monocyclic or polycyclic alicyclic hydrocarbon structure and is decomposed by the action of an acid to increase a solubility rate in an alkali developing solution.
2. The positive photosensitive composition as described in item (1) above, wherein the resin of component (B) contains a repeating unit having a lactone structure.
3. The positive photosensitive composition as described in item (1) or (2) above, wherein the compound of component (A1) is a sulfonium salt.
4. The positive photosensitive composition as described in any one of items (1) to (3) above, wherein the onium salt of component (A2) is a sulfonium salt, an iodonium salt or an ammonium salt.
The positive photosensitive composition according to the present invention will be described in more detail below.
 less than  less than Component (A1) greater than  greater than 
Any compound that generates an alkanesulfonic acid in which the xcex1-position is substituted with a fluorine atom upon irradiation of an actinic ray or radiation (hereinafter, also referred to as an acid generator) can be used as the compound of component (A1) in the present invention.
The compound that generates an alkanesulfonic acid in which the xcex1-position is substituted with a fluorine atom includes an onium salt, e.g., a sulfonium salt or an iodonium salt, an oxymesulfonate compound, an imidosulfonate compound and o-nitrobenzylsulfonate compound.
Preferred examples thereof include a sulfonium salt, which is composed of an anion portion and a cation portion, represented by the following formula (A1): 
In formula (A1), R1, R2 and R3, which may be the same or different, each independently represent an organic residue. A number of carbon atom included in the organic residue represented by R1, R2 or R3 is ordinarily from 1 to 30, and preferably from 1 to 20.
Alternatively, two of R1, R2 and R3 may be combined with each other to form a ring, and the ring may contain an oxygen atom, a sulfur atom, an ester bond, an amido bond or a carbonyl group. The group formed by combining two of R1, R 2 and R3 includes an alkylene group (e.g., butylene or pentylene group).
Specific examples of the organic residue represented by R1, R2 or R3 include corresponding groups in Compounds (A1-1), (A1-2) and (A1-3) described below.
Zxe2x88x92 represents a counter anion, specifically an alkanesulfonic acid anion in which the carbon atom at the xcex1-position is substituted with a fluorine atom and which is represented by RFSO3xe2x88x92.
The RF, which represents the alkane portion of the alkanesulfonic acid, is not particularly limited and includes a straight chain, branched or cyclic alkyl group having from 1 to 20 carbon atoms, e.g., methyl, ethyl, propyl, butyl, hexyl, octyl, dodecyl, tetradecyl or hexadecyl group, and preferably a straight chain, branched or cyclic alkyl group having from 4 to 16 carbon atoms.
At least one fluorine atom should be present at the xcex1-position of the alkanesulfonic acid, and the alkanesulfonic acid may also have other fluorine atoms in other portions thereof.
Preferred examples of the RF include a fluorine-substituted straight chain alkyl group represented by CF3(CF2)y, wherein y represents an integer of from 0 to 15, preferably an integer of from 1 to 9, and more preferably an integer of from 1 to 5. By using the fluorine-substituted straight chain alkyl group represented by CF3(CF2)y, excellent balance of sensitivity and resolution is achieved and change in performance with the passage of time from exposure to post heating is reduced.
Specific examples of the RF include CF3xe2x80x94, CF3CF2xe2x80x94, CF3CHFCF2xe2x80x94, CF3(CF2)2xe2x80x94, CF3(CF2)3xe2x80x94, CF3(CF2)4xe2x80x94, CF3(CF2)5xe2x80x94, CF3(CF2)7xe2x80x94, CF3(CF2)9xe2x80x94, CF3(CF2)11xe2x80x94, CF3(CF2)13xe2x80x94 and CF3(CF2)15xe2x80x94, preferably CF3CF2xe2x80x94, CF3(CF2)2xe2x80x94, CF3(CF2)3xe2x80x94, CF3(CF2)4xe2x80x94, CF3(CF2)5xe2x80x94, CF3(CF2)7xe2x80x94 and CF3(CF2)9xe2x80x94, more preferably CF3CF2xe2x80x94, CF3(CF2)2xe2x80x94, CF3(CF2)3xe2x80x94, CF3(CF2)4xe2x80x94 and CF3(CF2)5xe2x80x94, and particularly preferably CF3(CF2)3xe2x80x94.
The alkane portion may have a substituent. Examples of the substituent include an alkyl group, a hydroxy group, a halogen atom, an alkoxy group (preferably having from 1 to 5 carbon atoms, e.g., methoxy, ethoxy, propoxy or butoxy group), an alkoxycarbonyl group (preferably having from 2 to 6 carbon atoms, e.g., methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl or butoxycarbonyl group), an acyl group (preferably having from 2 to 15 carbon atoms), an acyloxy group (preferably having from 2 to 15 carbon atoms), an amino group, a carboxy group, an alkylsulfonylamino group (preferably having from 1 to 5 carbon atoms), an alkylsulfonyloxy group (preferably having from 1 to 5 carbon atoms), a cyano group and an oxo group.
The alkane portion may also have a connecting group in the alkyl chain. Preferred examples of the connecting group include an ester bond, an amido bond, a sulfonamido bond, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94 and a combination of two or more thereof.
A compound having two or more structures represented by formula (A1) may also be employed. Such a compound includes, for example, a compound wherein at least one of R1, R2 and R3 in the compound represented by formula (A1) is connected with at least one of R1, R2 and R3 in another compound represented by formula (A1).
Of the compounds of component (A1), Compounds (A1-1), (A1-2) and (A1-3) described below are preferred.
Now, Compound (A1-1) is described below.
Compound (A1-1) is a triarylsulfonium compound represented by formula (A1) wherein R1, R2 and R3 each represent an aryl group. Specifically, the compound has a triarylsulfonium as a cation.
The aryl group of the triarylsulfonium cation is preferably a phenyl group or a naphthyl group, and more preferably a phenyl group. Three aryl groups of the triarylsulfonium cation may be the same or different.
The aryl group may have a substituent, for example, an alkyl group (e.g., an alkyl group having from 1 to 15 carbon atoms), an alkoxy group (e.g., an alkoxy group having from 1 to 15 carbon atoms), a halogen atom, a hydroxy group or a phenylthio group. Preferred examples of the substituent include a straight chain, branched or cyclic alkyl group having from 1 to 12 carbon atoms and a straight chain, branched or cyclic alkoxy group having from 1 to 12 carbon atoms, and an alkyl group having from 1 to 4 carbon atoms and an alkoxy group having from 1 to 4 carbon atoms are most preferred. The substituent may be present on one of the three aryl groups. Also, the substituents may present on all of three aryl groups. It is preferred that the substituent is present on the p-position of aryl group.
The anion of triarylsulfonium compound is an alkanesulfonic acid anion in which the carbon atom at the xcex1-position is substituted with a fluorine atom and includes the above-described sulfonic acid anion. Preferred examples of the anion include a perfluoroalkanesulfonic acid anion having from 1 to 8 carbon atoms, and a perfluorobutanesulfonic acid anion, a perfluorooctanesulfonic acid anion, a trifluoromethanesulfonic acid anion and a perfluoroethoxyethanesulfonic acid anion are more preferred. By using such an alkanesulfonic acid anion, a decomposition rate of an acid-decomposable group is amplified to increase sensitivity, and diffusion of the acid generated is controlled to improve resolution.
The triarylsulfonium structure may be connected with another triarylsulfonium structure through a connecting group, e.g., xe2x80x94Sxe2x80x94 to form a compound having two or more of the triarylsulfonium structures.
Specific examples of the triarylsulfonium compound for use in the present invention are set forth below, but the present invention should not be construed as being limited thereto. 
Now, Compound (A1-2) is described below.
Compound (A1-2) is a compound represented by formula (A1) wherein R1, R2 and R3 each independently represent an organic residue that does not contain an aromatic ring. The term xe2x80x9caromatic ringxe2x80x9d used herein includes an aromatic ring containing a hetero atom.
The organic residue that does not contain an aromatic ring has ordinarily from 1 to 30 carbon atoms, and preferably from 1 to 20 carbon atoms.
In Compound (A1-2), R1, R2 and R3 each preferably represent an alkyl group, a 2-oxoalkyl group, an alkoxycarbonylmethyl group, an allyl group or a vinyl group, more preferably a straight chain, branched or cyclic 2-oxoalkyl group or an alkoxycarbonylmethyl group, and most preferably a straight chain or branched 2-oxoalkyl group.
The alkyl group represented by R1, R2 or R3 may be a straight chain, branched or cyclic alkyl group, and is preferably a straight chain or branched alkyl group having from 1 to 10 carbon atoms (e.g., methyl, ethyl, propyl, butyl or pentyl group) or a cyclic alkyl group having from 3 to 10 carbon atoms (e.g., cyclopentyl, cyclohexyl or norbornyl group).
The 2-oxoalkyl group represented by R1, R2 or R3 may be a straight chain, branched or cyclic 2-oxoalkyl group, and is preferably a group having  greater than Cxe2x95x90O on the 2-position of the alkyl group described above.
The alkoxy group in the alkoxycarbonylmethyl group is preferably an alkoxy group having from 1 to 5 carbon atoms (e.g., methoxy, ethoxy, propoxy, butoxy or pentoxy group).
The organic residue represented by. R1, R2 or R3 may be further substituted with a halogen atom, an alkoxy group (e.g., an alkoxy group having from 1 to 5 carbon atoms), a hydroxy group, a cyano group or a nitro group.
Alternatively, two of R1, R2 and R3 may be combined with each other to form a ring, and the ring may contain an oxygen atom, a sulfur atom, an ester bond, an amido bond or a carbonyl group. The group formed by combining two of R1, R2 and R3 includes an alkylene group (e.g., butylene or pentylene group).
It is preferred from the standpoint of photo reactivity that one of R1, R2 and R3 represents a group containing a carbon-carbon double bond or a carbon-oxygen double bond.
The anion of sulfonium compound having no aromatic ring is an alkanesulfonic acid anion in which the carbon atom at the xcex1-position is substituted with a fluorine atom and includes the above-described sulfonic acid anion. Preferred examples of the anion include a perfluoroalkanesulfonic acid anion having from 1 to 8 carbon atoms, and a perfluorobutanesulfonic acid anion and a perfluorooctanesulfonic acid anion are more preferred. By using such an alkanesulfonic acid anion, a decomposition rate of an acid-decomposable group is amplified to increase sensitivity, and diffusion of the acid generated is controlled to improve resolution.
Specific examples of the sulfonium compound having no aromatic ring for use in the present invention are set forth below, but the present invention should not be construed as being limited thereto. 
Now, Compound (A1-3) is described below.
Compound (A1-3) is a compound represented by formula (A1-3) shown below. Specifically, the compound has a phenacylsulfonium salt structure. 
In formula (A1-3), R1c to R5c, which may be the same or different, each independently represent a hydrogen atom, an alkyl group, an alkoxy group or a halogen atom.
R6c and R7c, which may be the same or different, each independently represent a hydrogen atom, an alkyl group or an aryl group.
Rx and Ry, which may be the same or different, each independently represent an alkyl group, a 2-oxoalkyl group, an alkoxycarbonylmethyl group, an allyl group or a vinyl group.
Two or more of R1c to R7c and Rx and Ry may be combined with each other to form a ring structure, respectively, and the ring structure may contain an oxygen atom, a sulfur atom, an ester bond or an amido bond.
Zcxe2x88x92 represents an alkanesulfonio acid anion in which the carbon atom at the xcex1-position is substituted with a fluorine atom.
The alkyl group represented by any one of R1c to R5c may be a straight chain, branched or cyclic alkyl group, includes, for example, an alkyl group having from 1 to 10 carbon atoms, and is preferably a straight chain or branched alkyl group having from 1 to 5 carbon atoms (e.g., methyl, ethyl, straight chain or branched propyl, straight chain or branched butyl or straight chain or branched pentyl group) or a cyclic alkyl group having from 3 to 8 carbon atoms (e.g., cyclopentyl or cyclohexyl group).
The alkoxy group represented by any one of R1c to R5c may be a straight chain, branched or cyclic alkoxy group, includes, for example, an alkoxy group having from 1 to 10 carbon atoms, and is preferably a straight chain or branched alkoxy group having from 1 to 5 carbon atoms (e.g., methoxy, ethoxy, straight chain or branched propoxy, straight chain or branched butoxy or straight chain or branched pentoxy group) or a cyclic alkoxy group having from 3 to 8 carbon atoms (e.g., cyclopentyloxy or cyclohexyloxy group).
Preferably, any one of R1c to R5c is a straight chain, branched or cyclic alkyl group or a straight chain, branched or cyclic alkoxy group, and more preferably, the total number of carbon atoms included in R1c to R5c is from 2 to 15. Using such a compound having an alkyl group or alkoxy group in any one of R1c to R5c, solvent solubility is further improved to restrain the occurrence of particles during preservation.
The alkyl group represented by R6c or R7c is sane as the alkyl group represented by any one of R1c to R5c. The aryl group represented by R6c or R7c includes, for example, an aryl group having from 6 to 14 carbon atoms (e.g., phenyl group).
The alkyl group represented by Rx or Ry is same as the alkyl group represented by any one of R1c to R5c.
The 2-oxoalkyl group represented by Rx or Ry includes a group having  greater than Cxe2x95x90O on the 2-position of the alkyl group represented by any one of R1c to R5c.
The alkoxy group in the alkoxycarbonylmethyl group represented by Rx or Ry is same as the alkoxy group represented by any one of R1c to R5c.
The group formed by connecting Rx and Ry includes, for example, butylene and pentylene groups.
Zcxe2x88x92 represents an alkanesulfonic acid anion in which the carbon atom at the xcex1-position is substituted with a fluorine atom and includes the above-described sulfonic acid anion. The alkane portion of the alkanesulfonic anion may be substituted with a substituent, for example, an alkoxy group (e.g., an alkoxy group having from 1 to 8 carbon atoms) or a perfluoroalkoxy group (e.g., a perfluoroalkoxy group having from 1 to 8 carbon atoms).
Zcxe2x88x92 preferably represents a perfluoroalkanesulfonic acid anion having from 1 to 8 carbon atoms, particularly preferably a perfluorooctanesulfonic acid anion, a perfluorobutanesulfonic acid anion or a trifluoromethanesulfonic acid anion, and most preferably a perfluorobutanesulfonic acid anion. By using such an alkanesulfonic acid anion, a decomposition rate of an acid-decomposable group is amplified to increase sensitivity, and diffusion of the acid generated is controlled to improve resolution.
Specific examples of the compound having the phenacylsulfonium salt structure for use in the present invention are set forth below, but the present invention should not be construed as being limited thereto. 
 less than  less than Component (A2) greater than  greater than 
Any onium salt of an alkanesulfonic acid in which the xcex1-position is not substituted with a fluorine atom can be used as the compound of component (A2) in the present invention. The compound of component (A2) is preferably a sulfonium salt, an iodonium salt or an ammonium salt.
Preferred examples of the compound of component (A2) include compounds represented by the following formulae (A2-1), (A2-2) and (A2-3). 
In the above formulae, R1d, R2d and R3d have the same meaning as defined for R1, R2 and R3 in formula (A1) described above, respectively.
R1e, R2e, R1f, R2f, R3f and R4f, which may be the same or different, each independently represent a substituted or unsaturated alkyl group or a substituted or unsaturated aryl group. The alkyl group is preferably an alkyl group having from 1 to 8 carbon atoms, The aryl group is preferably an aryl group having from 6 to 14 carbon atoms.
Also, R1f, R2f, R3f and R4f each may represent a hydrogen atom.
R1e and R2e each preferably represent a substituted or unsaturated aryl group. R1f, R2f, R3f and R4f each preferably represent a substituted or unsaturated alkyl group.
Preferred examples of the substituent for the aryl group include an alkoxy group having from 1 to 8 carbon atoms, an alkyl group having from 1 to 8 carbon atoms, a nitro group, a carboxy group, a hydroxy group and a halogen atom. Preferred examples of the substituent for the alkyl group include an alkoxy group having from 1 to 8 carbon atoms, a carboxy group, an alkoxycarbonyl group having from 2 to 9 carbon atoms and an alkoxyalkoxy group having from 2 to 9 carbon atoms.
Specific examples of the cation in the compound represented by formula (A2-1) include those described for the cations in the compounds represented by formulae (A1-1) to (A1-3).
An anion portion represented by Xxe2x88x92 is an alkanesulfonic acid anion in which the carbon atom at the xcex1-position is not substituted with a fluorine atom and represented by RSO3xe2x88x92.
The alkane portion of the alkanesulfonic acid represented by R is not particularly restricted and includes a straight chain, branched or cyclic alky group having from 1 to 20 carbon atoms, e.g., methyl, ethyl, propyl, butyl, hexyl, octyl, dodecyl, tetradecyl or hexadecyl group, and preferably a straight chain, branched or cyclic alkyl group having from 4 to 16 carbon atoms.
The alkane portion may have a substituent provided that it does not constitute the alkanesulfonic acid in which the carbon atom at the xcex1-position has a fluorine atom. Examples of the substituent include an alkyl group, a hydroxy group, a halogen atom, an alkoxy group (preferably having from 1 to 5 carbon atoms, e.g., methoxy, ethoxy, propoxy or butoxy group), an alkoxycarbonyl group (preferably having from 2 to 6 carbon atoms, e.g., methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl or butoxycarbonyl group), an acyl group (preferably having from 2 to 15 carbon atoms), an acyloxy group (preferably having from 2 to 15 carbon atoms), an amino group, a carboxy group, an alkylsulfonylamino group (preferably having from 1 to 5 carbon atoms), an alkylsulfonyloxy group (preferably having from 1 to 5 carbon atoms), a cyano group and an oxo group.
Preferred examples of the alkanesulfonic acid for Xxe2x88x92 include an alkanesulfonic acid having from 4 to 16 carbon atoms and an alkanesulfonic acid having a polycyclic alicyclic structure, e.g., camphorsulfonic acid.
Specific examples of the compound of component (A2) are set forth as A2-1-1 to A2-3-9 below, but the present invention should not be constued as being limited thereto. 
The content of component (A1) is ordinarily from 0.01 to 10% by weight, preferably from 0.1 to 7% by weight, and more preferably from 0.1 to 5% by weight, based on the total solid content of positive photosensitive composition.
The content of component (A2) is ordinarily from 0.01 to 10% by weight, preferably from 0.1 to 7% by weight, and more preferably from 0.1 to 5% by weight, based on the total solid content of positive photosensitive composition.
A weight ratio of the content of component (A1) to the content of component (A2) is ordinarily from 99/1 to 1/99, preferably from 99/1 to 30/70, and more preferably from 99/1 to 50/50. It is preferred that the content of component (A1) is larger than the content of component (A2).
The sulfonic acid in which the xcex1-position is substituted with a fluorine atom exhibits a high acidity and has a high ability for decomposing an acid-decomposable resin in comparison with the sulfonic acid in which the xcex1-position is not substituted with a fluorine atom. When a compound that generates a sulfonic acid in which the xcex1-position is substituted with a fluorine atom is used alone, a problem of inferior resolution and pitch dependency causes, while high sensitivity is achieved. On the other hand, when the sulfonium salt of sulfonic acid having no fluorine substituent is used as a photo-acid generator together with an alicyclic resin, a problem in that the sensitivity is severely decreased occurs, because the acid generated has a low ability for decomposing the resin. On the contrary, in case of using these two kinds of compounds in combination, the compound that generates a sulfonic acid in which the xcex1-position is substituted with a fluorine atom generates the sulfonic acid in which the xcex1-position is substituted with a fluorine atom upon exposure. The sulfonic acid in which the xcex1-position is substituted with a fluorine atom acts to decompose an acid-decomposable resin in a high efficiency and then encounters with the onium salt of sulfonic acid having no fluorine substituent, thereby forming an onium salt of sulfonic acid in which the xcex1-position is substituted with a fluorine atom and releasing a sulfonic acid having no fluorine substituent by means of salt exchange. Since the sulfonic acid having no fluorine substituent has a low ability for decomposing an acid-decomposable resin, diffusion of the acid-decomposing reaction is restrained. As a result, disturbance in exposure latent images due to the diffusion is controlled, and it is believed that the resolution and pitch dependency are improved without decrease in the sensitivity.
Acid Generating Compound Usable Together with the Compounds of Components (A1) and (A2)
A compound (photo-acid generator) that decomposes upon irradiation of an actinic ray or radiation to generate an acid other than the compounds of components (A1) and (A2) may be further used together in the present invention.
An amount of the photo-acid generator used together with the compounds of components (A1) and (A2) according to the present invention is ordinarily from 100/0 to 20/80, preferably from 100/0 to 40/60, and more preferably from 100/0 to 50/50, in terms of a molar ratio of compounds of components (A1) and (A2)/other photo-acid generators.
Such a photo-acid generator used together with the compounds of components (A1) and (A2) can be appropriately selected from photoinitiators for photo-cationic polymerization, photoinitiators for photo-radical polymerization, photo-achromatic agents for dyes, photo-discoloring agents, known compounds generating an acid upon irradiation of an actinic ray or radiation used for microresists, and mixtures thereof.
Examples of such photo-acid generators include a diazonium salt, a phosphonium salt, a sulfonium salt, an iodonium salt, an imidosulfonate, an oxymesulfonate, a diazodisulfone, a disulfone and an o-nitrobenzylsulfonate.
Also, polymer compounds in which a group or compound generating an acid upon irradiation of an actinic ray or radiation is introduced into the main chain or side chain thereof, for example, compounds as described, for example, in U.S. Pat. No. 3,849,137, West German Patent 3,914,407, JP-A-63-26653, JP-A-55-164824, JP-A-62-69263, JP-A-63-146038, JP-A-63-163452, JP-A-62-153853 and JP-A-63-146029 can be used.
Further, compounds generating an acid with light as described, for example, in U.S. Pat. No. 3,779,778 and European Patent 126,712 can be used.
Particularly preferred examples of the photo-acid generator used together with the compounds of components (A1) and (A2) according to the present invention are set forth below. 
 less than  less than (B) Resin Increasing a Solubility Rate in an Alkali Developing Solution by the Action of an Acid (Hereinafter, also Referred to as an xe2x80x9cAcid-decomposable Resinxe2x80x9d) greater than  greater than 
Any resin that has a monocyclic or polycyclic alicyclic hydrocarbon structure and is decomposed by the action of an acid to increase a solubility rate in an alkali developing solution can be used as the acid-decomposable resin of component (B). Preferred examples of the resin of component (B) include resins containing at least one repeating unit selected from a repeating unit having a partial structure including an alicyclic hydrocarbon represented by formula (pI), (pII), (pIII), (pIV), (pV) or (pVI) described below and a repeating unit represented by formula (II) described below. 
In the above formulae, R11, represents a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group or a sec-butyl group, and Z represents an atomic group necessary for forming an alicyclic hydrocarbon group together with the carbon atom.
R12 to R16 each independently represent a straight chain or branched alkyl group having from 1 to 4 carbon atoms or an alicyclic hydrocarbon group, provided that at least one of R12 to R14, and either R15 or R16 represents an alicyclic hydrocarbon group.
R17 to R21 each independently represent a hydrogen atom, a straight chain or branched alkyl group having from 1 to 4 carbon atoms or an alicyclic hydrocarbon group, provided that at least one of R17 to R21 represents an alicyclic hydrocarbon group, and either R19 or R21 represents a straight chain or branched alkyl group having from 1 to 4 carbon atoms or an alicyclic hydrocarbon group.
R22 to R25 each independently represent a straight chain or branched alkyl group having from 1 to 4 carbon atoms or an alicyclic hydrocarbon group, provided that at least one of R22 to R25 represents an alicyclic hydrocarbon group, Alternatively, R23 and R24 may be combined with each other to form a ring. 
In formula (II), R11xe2x80x2 and R12xe2x80x2, which may be the same or different, each independently represent a hydrogen atom, a cyano group, a halogen atom or an alkyl group which may have a substituent.
Zxe2x80x2 represents an atomic group necessary for forming an alicyclic structure, which may be substituted, together with the connected two carbon atoms (Cxe2x80x94C).
Of the repeating units represented by formula (II), those represented by formulae (II-A) and (II-B) shown below are more preferred. 
In formulae (II-A) and (II-B), R13xe2x80x2 to R16xe2x80x2, which may be the same or different, each independently represents a hydrogen atom, a halogen atom, a cyano group, xe2x80x94COOS, xe2x80x94COOR5, a group capable of decomposing by the action of acid, xe2x80x94C(xe2x95x90O)xe2x80x94Xxe2x80x94Axe2x80x2xe2x80x94R17xe2x80x2, an alkyl group which may have a substituent or a cyclic hydrocarbon group which may have a substituent.
R5 represents an alkyl group which may have a substituent, a cyclic hydrocarbon group which may have a substituent or a group represented by Y.
X represents an oxygen atom, a sulfur atom, xe2x80x94NHxe2x80x94, xe2x80x94NHSO2xe2x80x94 or xe2x80x94NHSO2NHxe2x80x94.
Axe2x80x2 represents a single bond or a divalent linkage group.
Alternatively, at least two of R13xe2x80x2 to R16xe2x80x2 may be combined with each other to form a ring, n represents 0 or 1.
R17xe2x80x2 represents xe2x80x94COOH, xe2x80x94COOR5, xe2x80x94CN, a hydroxy group, an alkoxy group which may have a substituent, xe2x80x94COxe2x80x94NHxe2x80x94R6, xe2x80x94COxe2x80x94NHxe2x80x94SO2xe2x80x94R6 or a group represented by Y. R6 represents an alkyl group which may have a substituent or a cyclic hydrocarbon group which may have a substituent.
The group represented by Y has the following formula: 
wherein R21xe2x80x2 to R30xe2x80x2, which may be the same or different, each independently represents a hydrogen atom or an alkyl group which may have a substituent, and a and b each represent 1 or 2.
In formulae (pI) to (pVI), the alkyl group for R12 to R25 includes a straight chain or branched alkyl group having from 1 to 4 carbon atoms, which may be substituted. Examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and tert-butyl groups.
Examples of the substituent for the alkyl group include an alkoxy group having from 1 to 4 carbon atoms, a halogen atom (e.g., fluorine, chlorine, bromine or iodine atom), an acyl group, an acyloxy group, a cyano group, a hydroxy group, a carboxy group, an alkoxycarbonyl group and a nitro group.
The alicyclic hydrocarbon group in R11 to R25 or the alicyclic hydrocarbon group formed by Z and the carbon atoms may be a monocyclic group or a polycyclic group, and includes specifically a group having not less than 5 carbon atoms and including, for example, a amonocyclic, bicyclic, tricyclic or tetracyclic structure. The number of carbon atoms included is preferably from 6 to 30, and more preferably from 7 to 25. The alicyclic hydrocarbon group may have a substituent.
Examples of the structure of alicyclic portion in the alicyclic hydrocarbon group are set forth below. 
Preferred examples of the alicyclic portion for use in the present invention include an adamantyl group, a noradamantyl group, a decalin residue, a tricyclodecanyl group, a tetracyclododecanyl group, a norbornyl group, a cedrol group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclodecanyl group and a cyclododecanyl group. Of these groups, an adamantyl group, a decalin residue, a norbornyl group, a cedrol group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclodecanyl group and a cyclododecanyl group are more preferred.
Examples of the substituent for the alicyclic hydrocarbon group include an alkyl group, a substituted alkyl group, a halogen atom, a hydroxy group, an alkoxy group, a carboxy group and an alkoxycarbonyl group. The alkyl group is preferably a lower alkyl group, for example, methyl, ethyl, propyl, isopropyl or butyl group, and more preferably methyl, ethyl, propyl or isopropyl group. Examples of the substituent for the substituted alkyl group include a hydroxy group, a halogen atom and an alkoxy group. The alkoxy group includes an alkoxy group having from 1 to 4 carbon atoms, for example, methoxy, ethoxy, propoxy or butoxy group.
The structure represented by any one of formulae (pI) to (pVI) in the resin can be used for protecting an alkali-soluble group. The alkali-soluble group includes various groups known in the field of art.
Specific examples of the alkali-soluble group include a carboxylic acid group, a sulfonic acid group, a phenol group and a thiophenol group, and a carboxylic acid group and a sulfonic acid group are preferably used.
The alkali-soluble group protected by the structure represented by any one of formulae (pI) to (pVI) in the resin preferably includes groups represented by the following formulae (pVII) to (pXI): 
In the above formulae, R11 to R25 and Z has the same meanings as defined above, respectively.
A repeating unit having the alkali-soluble group protected by the structure represented by any one of formulae (pI) to (pVI) in the resin is preferably represented by the following formula (pA): 
In the formula, R""s, which may be the same or different, each represent a hydrogen atom, a halogen atom or a straight chain or branched alkyl group having from 1 to 4 carbon atoms, which may be substituted.
A represents a single bond, an alkylene group, a substituted alkylene group, an ether group, a thioether group, a carbonyl group, an ester group, an amido group, a sulfonamido group, a urethane group, a urea group or a combination of two or more thereof.
Ra represents any one of the groups represented by formulae (pI) to (pVI).
Specific examples of the monomer corresponding to the repeating unit represented by formula (pA) are set forth below, but the present invention should not be construed as being limited thereto. 
In formula (II), R11xe2x80x2 and R12xe2x80x2, which may be the same or different, each independently represent a hydrogen atom, a cyano group, a halogen atom or an alkyl group which may have a substituent.
Zxe2x80x2 represents an atomic group necessary for forming an alicyclic structure, which may be substituted, together with the connected two carbon atoms (Cxe2x80x94C).
The halogen atom for R11xe2x80x2 or R12xe2x80x2 includes, for example, chlorine, bromine, fluorine and iodine atoms.
The alkyl group for each of R11xe2x80x2, R12xe2x80x2 and R21xe2x80x2 to R30xe2x80x2 includes preferably a straight chain or branched alkyl group having from 1 to 10 carbon atoms, more preferably a straight chain or branched alkyl group having from 1 to 6 carbon atoms, and still more preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and tert-butyl groups.
Examples of the substituent for the alkyl group include a hydroxy group, a halogen atom, a carboxy group, an alkoxy group, an acyl group, a cyano group and an acyloxy group. The halogen atom includes chlorine, bromine, fluorine and iodine atoms. The alkoxy group includes an alkoxy group having from 1 to 4 carbon atoms, for example, methoxy, ethoxy, propoxy or butoxy group. The acyl group includes, for example, formyl or acetyl group. The acyloxy group includes, for example, an acetoxy group.
The atomic group necessary for forming an alicyclic structure represented by Zxe2x80x2 is an atomic group necessary for forming a repeating unit of alicyclic hydrocarbon moiety, which may be substituted. In particular, an atomic group necessary for forming a bridged alicyclic structure, by which a repeating unit of the bridged alicyclic hydrocarbon is completed, is preferred.
The skeleton of the bridged alicyclic hydrocarbon formed includes those described below. 
Of the skeletons of the bridged alicyclic hydrocarbon described above, (5), (6), (7), (9), (10) , (13), (14), (15), (23), (28), (36), (37), (42) and (47) are preferred.
The skeleton of the alicyclic hydrocarbon may have a substituent. Examples of the substituent include the atoms and groups represented by R13xe2x80x2 to R16xe2x80x2 in formula (II-A) or (II-B).
Of the repeating units containing the bridged alicyclic hydrocarbon, those represented by formulae (II-A) and (II-B) described above are more preferred.
In formulae (II-A) and (II-B), R13xe2x80x2 to R16xe2x80x2, which may be the same or different, each independently represents a hydrogen atom, a halogen atom, a cyano group, xe2x80x94COOH, xe2x80x94COOR5, a group capable of decomposing by the action of acid, xe2x80x94C(xe2x95x90O)xe2x80x94Xxe2x80x94Axe2x80x2xe2x80x94R17xe2x80x2, an alkyl group which may have a substituent or a cyclic hydrocarbon group which may have a substituent.
R5 represents an alkyl group which may have a substituent, a cyclic hydrocarbon group which may have a substituent or a group represented by Y.
X represents an oxygen atom, a sulfur atom, xe2x80x94NHxe2x80x94, xe2x80x94NHSO2xe2x80x94or xe2x80x94NHSO2NHxe2x80x94.
Axe2x80x2 represents a single bond or a divalent linkage group.
Alternatively, at least two of R13xe2x80x2 to R16xe2x80x2 may be combined with each other to form a ring. n represents 0 or 1.
R17xe2x80x2 represents xe2x80x94COOH, xe2x80x94COOR5, xe2x80x94CN, a hydroxy group, an alkoxy group which may have a substituent, xe2x80x94COxe2x80x94NHxe2x80x94R6, xe2x80x94COxe2x80x94NHxe2x80x94SO2xe2x80x94R6 or a group represented by Y. R6 represents an alkyl group which may have a substituent or a cyclic hydrocarbon group which may have a substituent.
In the group represented by Y, R21xe2x80x2 to R30xe2x80x2, which may be the same or different, each independently represents a hydrogen atom or an alkyl group which may have a substituent, and a and b each represent 1 or 2.
In the resin according to the present invention, an acid-decomposable group may be incorporated into the above described xe2x80x94C(xe2x95x90O)xe2x80x94Xxe2x80x94Axe2x80x2xe2x80x94R17xe2x80x2 or as a substituent for Zxe2x80x2 in formula (II).
The acid-decomposable group includes a group represented by the following formula:
xe2x80x94C(xe2x95x90O)xe2x80x94X1xe2x80x94R0
In the formula, R0 represents a tertiary alkyl group, for example, tert-butyl or tert-amyl group, an isobornyl group, an 1-alkoxyethyl group, for example, 1-ethoxyethyl, 1-butoxyethyl, 1-isobutoxyethyl or 1-cyclohexyloxyethyl group, an alkoxymethyl group, for example, 1-metoxymethyl or 1-ethoxymethyl group, a 3-oxoalkyl group, a tetrahydropyranyl group, a tetrahydrofuryl group, a trialkylsilyl ester group, a 3-oxocyclohexyl ester group, a 2-methyl-2-adamantyl group or a mevalonic lactone residue, and X1 has the same meaning as X defined above.
The halogen atom for each of R13xe2x80x2 or R16xe2x80x2 includes, for example, chlorine, bromine, fluorine and iodine atoms.
The alkyl group for each of R5, R6 and R13xe2x80x2 to R16xe2x80x2 includes preferably a straight chain or branched alkyl group having from 1 to 10 carbon atoms, more preferably a straight chain or branched alkyl group having from 1 to 6 carbon atoms, and still more preferably methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl and tert-butyl groups.
The cyclic hydrocarbon group for each of R5, R6 and R13xe2x80x2 to R16xe2x80x2 includes a cyclic alkyl group and a bridged hydrocarbon moiety, for example, cyclopropyl, cyclopentyl, cyclohexyl, adamantyl, 2-methyl-2-adamantyl, norbornyl, bornyl, isobornyl, tricyclodecanyl, dicyclopentenyl, norbornaneepoxy, menthyl, isomenthyl, neomenthyl or tetracyclododecanyl group.
The ring formed by combining at least two of R13xe2x80x2 to R16xe2x80x2 includes a ring having from 5 to 12 carbon atoms, for example, cyclopentene, cyclohexene, cycloheptane or cyclooctane ring.
The alkoxy group for R17xe2x80x2 includes an alkoxy group having from 1 to 4 carbon atoms, for example, methoxy, ethoxy, propoxy or butoxy group.
Examples of the substituent for the alkyl group, cyclic hydrocarbon group or alkoxy group described above include a hydroxy group, a halogen atom, a carboxy group, an alkoxy group, an acyl group, a cyano group, an acyloxy group, an alkyl group and a cyclic hydrocarbon group. The halogen atom includes, for example, chlorine, bromine, fluorine and iodine atoms. The alkoxy group includes an alkoxy group having from 1 to 4 carbon atoms, for example, methoxy, ethoxy, propoxy or butoxy group. The acyl group includes, for example, formyl and acetyl groups. The acyloxy group includes, for example, an acetoxy group.
The alkyl group and cyclic hydrocarbon group include those described above.
The divalent linkage group for Axe2x80x2 includes a single bond, an alkylene group, a substituted alkylene group, an ether group, a thioether group, a carbonyl group, an ester group, an amido group, a sulfonamido group, a urethane group, a urea group and a combination of two or more thereof.
Examples of the alkylene group or substituted alkylene group for Axe2x80x2 include a group represented by the following formula:
xe2x80x94{C(Ra)(Rb)}rxe2x80x94
In the formula, Ra and Rb, which may be the same or different, each represent a hydrogen atom, an alkyl group, a substituted alkyl group, a halogen atom, a hydroxy group or an alkoxy group, and r represents an integer of from 1 to 10.
The alkyl group includes preferably a lower alkyl group, for example, methyl, ethyl, propyl, isopropyl or butyl group, and more preferably methyl, ethyl, propyl or isopropyl group. Examples of the substituent for the substituted alkyl group include a hydroxy group, a halogen atom and an alkoxy group. The alkoxy group includes an alkoxy group having from 1 to 4 carbon atoms, for example, methoxy, ethoxy, propoxy or butoxy group. The halogen atom includes, for example, chlorine, bromine, fluorine and iodine atoms.
In the resin of component (B) according to the present invention, the acid-decomposable group may be incorporated into at least one repeating unit selected from the repeating unit having a partial structure including an alicyclic hydrocarbon represented by formula (pI), (pII), (pIII), (pIV), (pV) or (pVI), the repeating unit represented by formula (II), and a repeating unit of a copolymerization component described hereinafter.
Various atoms and groups represented by R13xe2x80x2 to R16xe2x80x2 in formula (II-A) or (II-B) constitute substituents for the atomic group necessary for forming an alicyclic structure or a bridged alicyclic structure represented by Zxe2x80x2 in formula (II).
Specific examples of the repeating unit represented by formula (II-A) or (II-B) are set forth below as [II-1] to [II-175], but the present invention should not be construed as being limited thereto. 
It is preferred that the acid-decomposable resin of component (B) according to the present invention contains a repeating unit having a lactone structure.
For instance, the acid-decomposable resin preferably contains a repeating unit represented by the following formula (IV): 
In formula (IV), R1a represents a hydrogen atom or a methyl group.
W1 represents a single bond, an alkylene group, an ether group, a thioether group, a carbonyl group, an ester group or a combination of two or more thereof.
Ra1, Rb1, Rc1, Rd1 and Re1, which may be the same or different, each independently represent a hydrogen atom or an alkyl group having from 1 to 4 carbon atoms. m and n, which may be the same or different, each independently represent an integer of from 0 to 3, provided that the sum total of m and n is from 2 to 6.
The alkyl group having from 1 to 4 carbon atoms represented by Ra1, Rb1, Rc1, Rd1 or Re1 includes, for example, methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl and tert-butyl groups.
The alkylene group represented by W1 in formula (IV) includes a group represented by the following formula:
xe2x80x94{C(Rf)(Rg)}r1xe2x80x94
In the above formula, Rf and Rg, which may be the same or different, each represent a hydrogen atom, an alkyl group, a substituted alkyl group, a halogen atom, a hydroxy group or an alkoxy group, and r1 represents an integer of from 1 to 10.
The alkyl group is preferably a lower alkyl group, for example, methyl, ethyl, propyl, isopropyl or butyl group, more preferably methyl, ethyl, propyl or isopropyl group. A substituent for the substituted alkyl group includes, for example, a hydroxy group, a halogen atom and an alkoxy group. The alkoxy group includes an alkoxy group having from 1 to 4 carbon atoms, for example, methoxy, ethoxy, propoxy or butoxy group. The halogen atom includes, for example, chlorine, bromine, fluorine and iodine atoms.
Examples of further substituent for the alkyl group include a carboxy group, an acyloxy group, a cyano group, an alkyl group, a substituted alkyl group, a halogen atom, a hydroxy group, an alkoxy group, a substituted alkoxy group, an acetylamido group, an alkoxycarbonyl group and an acyl group.
The alkyl group includes a lower alkyl group, for example, methyl, ethyl, propyl, isopropyl, butyl, cyclopropyl, cyclobutyl or cyclopentyl group. A substituent for the substituted alkyl group includes, for example, a hydroxy group, a halogen atom and an alkoxy group. A substituent for the substituted alkoxy group includes, for example, an alkoxy group. The alkoxy group includes an alkoxy group having from 1 to 4 carbon atoms, for example, methoxy, ethoxy, propoxy or butoxy group. The acyloxy group includes, for example, an acetoxy group. The halogen atom includes, for example, chlorine, bromine, fluorine and iodine atoms.
Specific examples of the repeating unit represented by formula (IV) are set forth below, but the present invention should not be construed as being limited thereto. 
Of the specific examples of the repeating unit represented by formula (VI), (IV-17) to (IV-36) are preferred in view of more improved exposure margin.
Further, the repeating units represented by formula (IV) wherein an acrylate structure is included are preferred from a standpoint of good edge roughness.
It is also preferred that the resin according to the present invention contains a repeating unit including an alicyclic lactone structure represented by any one of the following formulae (V-1) to (V-4): 
In formulae (V-1) to (V-4), R1b, R2b, R3b, R4b and R5b, which may be the same or different, each independently represent a hydrogen atom, an alkyl group which may have a substitutent, a cycloalkyl group which may have a substituent or an alkenyl group which may have a substituent, or two of R1b, R2b, R3b, R4b and R5b may be combined with each other to form a ring.
The alkyl group represented by any one of R1b, R2b, R3b, R4b and R5b in formulae (V-1) to (V-4) includes a straight chain or branched alkyl group which may have a substituent. The straight chain or branched alkyl group includes preferably a straight chain or branched alkyl group having from 1 to 12 carbon atoms, more preferably a straight chain or branched alkyl group having from 1 to 10 carbon atoms, and still more preferably methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, nonyl and decyl groups.
The cycloalkyl group represented by any one of R1b, R2b, R3b, R4b and R5b in formulae (V-1) to (V-4) includes preferably a cycloalkyl group having from 3 to 8 carbon atoms, for example, cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl or cyclooctyl group.
The alkenyl group represented by any one of R1b, R2b, R3b, R4b and R5b in formulae (V-1) to (V-4) includes preferably an alkenyl group having from 2 to 6 carbon atoms, for example, vinyl, propenyl, butenyl or hexenyl group.
The ring formed by combining two of R1b, R2b, R3b, R4b and R5b in any one of formulae (V-1) to (V-4) includes preferably a 3-membered to 8-membered ring, for example, cyclopropane, cyclobutane, cyclopentane, cyclohexane or cyclooctane ring.
The group represented by R1b, R2b, R3b, R4b and R5b in formulae (V-1) to (V-4) can be bonded to any one of the carbon atoms constituting the cyclic structure.
Preferred examples of the substituent for the alkyl group, cycloalkyl group and alkenyl group described above include an alkoxy group having from 1 to 4 carbon atoms, a halogen atom (e.g., fluorine, chlorine, bromine or iodine atom), an acyl group having from 2 to 5 carbon atoms, an acyloxy group having from 2 to 5 carbon atoms, a cyano group, a hydroxy group, a carboxy group, an alkoxycarbonyl group having from 2 to 5 carbon atoms and a nitro group.
Examples of repeating unit having the group represented by any one of formulae (V-1) to (V-4) include a repeating unit represented by formula (II-A) or (II-B) described above wherein one of R13xe2x80x2 to R16xe2x80x2 has the group represented by any one of formulae (V-1) to (V-4), for example, R5 of xe2x80x94COOR5 is the group represented by any one of formulae (V-1) to (V-4), and a repeating unit represented by the following formula (AI): 
In formula (AI), Rb0 represents a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having from 1 to 4 carbon atoms. Preferred examples of the substituent for the alkyl group represented by Rb0 include the preferred examples of substituent for the alkyl group represented by R1b in any one of formulae (V-1) to (V-4) described above.
The halogen atom represented by Rb0 includes fluorine, chlorine, bromine and iodine atoms. Rb0 is preferably a hydrogen atom,
Axe2x80x2 in formula (AI) represents a single bond, an ether group, an ester group, a carbonyl group, an alkylene group or a divalent group formed by combining these groups.
B2 in formula (AI) represents the group represented by any one of formulae (V-1) to (V-4).
Examples of the divalent group formed by combination of the groups represented by Axe2x80x2 includes groups represented by the following formulae; 
In the above-described formulae, Rab and Rbb, which may be the same or different, each represent a hydrogen atom, an alkyl group, a substituted alkyl group, a halogen atom, a hydroxy group or an alkoxy group.
The alkyl group represented by any one of Rab and Rbb is preferably a lower alkyl group, for example, methyl, ethyl, propyl, isopropyl or butyl group, and more preferably methyl, ethyl, propyl or isopropyl group. A substituent for the substituted alkyl group includes a hydroxy group, a halogen atom and an alkoxy group having from 1 to 4 carbon atoms.
The alkoxy group includes an alkoxy group having from 1 to 4 carbon atoms, for example, methoxy, ethoxy, propoxy or butoxy group. The halogen atom includes, for example, chlorine, bromine, fluorine and iodine atoms, r1 represents an integer of from 1 to 10, and preferably from 1 to 4. m represents an integer of from 1 to 3, and preferably 1 or 2.
Specific examples of the repeating unit represented by formula (AI) are set forth below, but the present invention should not be construed as being limited thereto. 
It is also preferred that the acid-decomposable resin according to the present invention contains a repeating unit represented by the following formula (VI): 
In formula (VI), A6 represents a single bond, an alkylene group, a cycloalkylene group, an ether group, a thioether group, a carbonyl group, an ester group or a combination of two or more thereof.
R6a represents a hydrogen atom, an alkyl group having from 1 to 4 carbon atoms, a cyano group or a halogen atom.
The alkylene group for A6 in formula (VI) includes a group represented by the following formula:
xe2x80x94{C(Rnf)(Rng)}rxe2x80x94
In formula, Rnf and Rng, which may be the same or different, each represent a hydrogen atom, an alkyl group, a substituted alkyl group, a halogen atom, a hydroxy group or an alkoxy group, and r represents an integer of from 1 to 10.
The alkyl group is preferably a lower alkyl group, for example, methyl, ethyl, propyl, isopropyl or butyl group, and more preferably methyl, ethyl, propyl or isopropyl group. A substituent for the substituted alkyl group includes, for example, a hydroxy group, a halogen atom and an alkoxy group. The alkoxy group includes an alkoxy group having from 1 to 4 carbon atoms, for example, methoxy, ethoxy, propoxy or butoxy group. The halogen atom includes, for example, chlorine, bromine, fluorine and iodine atoms.
The cycloalkylene group represented by A6 in formula (VI) includes a cycloalkylene group having from 3 to 10 carbon atoms, for example, cyclopentylene, cyclohexylene or cyclooctylene group.
In formula (VI), the bridged alicyclic group including Z6 may have one or more substituents. Examples of the substituent include a halogen atom, an alkoxy group (preferably an alkoxy group having from 1 to 4 carbon atoms), an alkoxycarbonyl group (preferably an alkoxycarbonyl group having from 1 to 5 carbon atoms), an acyl group (for example, formyl or benzyl group), an acyloxy group (for example, propylcarbonyloxy or benzoyloxy group), an alkyl group (preferably an alkyl group having from 1 to 4 carbon atoms), a carboxy group, a hydroxy group and an alkylsulfonylsulfamoyl group (for example, xe2x80x94CONHSO2CH3). The alkyl group as the substituent may further be substituted with a hydroxy group, a halogen atom or an alkoxy group (preferably an alkoxy group having from 1 to 4 carbon atoms).
The oxygen atom of the ester group connected to A6 in formula (VI) can be bonded to any one of the carbon atoms constituting the bridged alicyclic structure containing Z6.
Specific examples of the repeating unit represented by formula (VI) are set forth below, but the present invention should not be construed as being limited thereto. 
The resin according to the present invention may further contain a repeating unit having a group represented by the following formulae (VII): 
In formula (VII), R2c, R3c and R4c, which may be the same or different, each represent a hydrogen atom or a hydroxy group, provided that at least one of R2c, R3c and R4c represents a hydroxy group.
The group represented by formula (VII) is preferably a dihydroxy body or a monohydroxy body, and more preferably a dihydroxy body.
Examples of the repeating unit having the group represented by formulae (VII) include a repeating unit represented by formula (II-A) or (II-B) described above wherein one of R13xe2x80x2 to R16xe2x80x2 has the group represented by formula (VII), for example, R5 of xe2x80x94COOR5 is the group represented by formula (VII), and a repeating unit represented by the following formula (AII): 
In formula (AII), R1c represents a hydrogen atom or a methyl group, and R2c, R3c and R4c, which may be the same or different, each independently represents a hydrogen atom or a hydroxy group, provided that at least one of R2c, R3c and R4c represents a hydroxy group.
Specific examples of the repeating unit represented by formula (AII) are set forth below, but the present invention should not be construed as being limited thereto. 
The resin according to the present invention may further contain a repeating unit having a group represented by the following formulae (VIII): 
In formula (VIII), Z2 represents xe2x80x94Oxe2x80x94 or xe2x80x94N(R41)xe2x80x94, R41 represents a hydrogen atom, a hydroxy group, an alkyl group, a haloalkyl group or xe2x80x94Oxe2x80x94SO2xe2x80x94R42, and R42 represents an alkyl group, a haloakyl group, a cycloalkyl group or a camphol residue.
Examples of the alkyl group represented by R41 or R42 include preferably a straight chain or branched alkyl group having form 1 to 10 carbon atoms, more preferably a straight chain or branched alkyl group having form 1 to 6 carbon atoms, and still more preferably methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl and tert-butyl groups.
Examples of the haloalkyl group represented by R41 or R42 include trifluoromethyl, nonafluorobutyl, pentadecafluorooctyl and trichloroinethyl groups.
Examples of the cycloalkyl group represented by R42 include cyclopentyl, cyclohexyl and cyclooctyl groups.
The alkyl group and haloalkyl group represented by R41 or R42 and the cycloalkyl group and camphol residue represented by R42 may have one or more substituents.
Examples of the substituent for the alkyl group, haloalkyl group, cycloalkyl group and camphol residue include a hydroxy group, a carboxy group, a cyano group, a halogen atom (e.g., chlorine, bromine, fluorine or iodine atom), an alkoxy group (preferably an alkoxy group having from 1 to 4 carbon atoms, e.g., methoxy, ethoxy, propoxy or butoxy group), an acyl group (preferably an acyl group having from 2 to 5 carbon atoms, e.g., formyl or acetyl group), an acyloxy group (preferably an acyloxy group having from 2 to 5 carbon atoms, e.g., acetoxy group) and an aryl group (preferably an aryl group having from 6 to 14 carbon atoms, e.g., phenyl group).
Specific examples of the repeating unit represented by formula (VIII) are set forth below as formulae [Ixe2x80x2-1] to [Ixe2x80x2-7], but the present invention should not be construed as being limited thereto. 
The acid-decomposable resin of component (B) according to the present invention may contain various repeating structural units in addition to the repeating structural units described above for the purposes of adjusting dry etching resistance, standard developing solution aptitude, adhesion to substrate, resist profile, and other characteristics ordinarily required for resist, for example, resolution, heat resistance and sensitivity.
Examples of such repeating structural units include repeating structural units corresponding to monomers described below, but the present invention should not be construed as being limited thereto.
The introduction of additional repeating structural unit makes possible the minute control of characteristics required for the acid-decomposable resin, particularly (1) solubility in a coating solvent, (2) film forming property (glass transition temperature), (3) developing property with alkali, (4) reduction in a film thickness (hydrophobicity, selection of alkali-soluble group), (5) adhesion of the unexposed area to a substrate, and (6) dry etching resistance.
Examples of such monomers include compounds having one addition-polymerizable unsaturated bond, for example, acrylates, methacrylate, acrylamides, methacrylamides, allyl compound, vinyl ethers and vinyl esters.
Specific examples of the monomer include an acrylate, for example, an alkyl acrylate (preferably an alkyl acrylate containing an alkyl group having from 1 to 10 carbon atoms), e.g., methyl acrylate, ethyl acrylate, propyl acrylate, amyl acrylate, cyclohexyl acrylate, ethylhexyl acrylate, octyl acrylate, tert-octyl acrylate, chloroethyl acrylate, 2-hydroxyethyl acrylate, 2,2-dimethylhydroxypropyl acrylate, 5-hydroxypentyl acrylate, trimethylolpropane monoacrylate, pentaerythritol monoacrylate, benzyl acrylate, methoxybenzyl acrylate, furfuryl acrylate or tetrahydrofurfuryl acrylate; a methacrylate, for example, an alkyl methacrylate (preferably an alkyl methacrylate containing an alkyl group having form 1 to 10 carbon atoms), e.g., methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, amyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, chlorobenzyl methacrylate, octyl methacrylate, 2-hydroxyethyl methacrylate, 4-hydroxybutyl methacrylate, 5-hydroxypentyl methacrylate, 2,2-dimethyl-3-hydroxypropyl methacrylate, trimethylolpropane monomethacrylate, pentaerythritol monomethacrylate, furfuryl methacrylate or tetrahydrofurfuryl methacrylate; an acrylamide, for example, acrylamide, an N-alkylacrylamide (the alkyl group of which is an alkyl group having from 1 to 10 carbon atoms, e.g., methyl, ethyl, propyl, butyl, tert-butyl, heptyl, octyl, cyclohexyl or hydroxyethyl group), an N,N-dialkylacrylamide (the alkyl group of which is an alkyl group having form 1 to 10 carbon atoms, e.g., methyl, ethyl, butyl, isobutyl, ethylhexyl or cyclohexyl group), N-hydroxyethyl-N-methylacrylamide and N-2-acetamidoethyl-N-acetylacrylamide; a methacrylamide, for example, methacrylamide, an N-alkylmethacrylamide (the alkyl group of which is an alkyl group having from 1 to 10 carbon atoms, e.g., methyl, ethyl, tert-butyl, ethylhexyl, hydroxyethyl or cyclohexyl group), an N,N-dialkylmethacrylamide (the alkyl group of which includes, e.g., ethyl, propyl and butyl groups) and N-hydroxyethyl-N-methylmethacrylamide; an allyl compound, for example, an allyl ester (e.g., allyl acetate, allyl caproate, ally caprate, allyl laurate, allyl palmitate, allyl stearate, allyl benzoate, allyl acetoacetate or ally lactate) and allyl oxyethanol; a vinyl ether, for example, an alkyl vinyl ether (e.g., hexyl vinyl ether, octyl vinyl ether, decyl vinyl ether, ethylhexyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, chloroethyl vinyl ether, 1-methyl-2,2-dimethylpropyl vinyl ether, 2-ethylbutyl vinyl ether, hydroxyethyl vinyl ether, diethylene glycol vinyl ether, dimethylaminoethyl vinyl ether, diethylaminoethyl vinyl ether, butylarninoethyl vinyl ether, benzyl vinyl ether or tetrahydrofurfuryl vinyl ether); a vinyl ester, for example, vinyl butyrate, vinyl isobutyrate, vinyl trimethylacetate, vinyl diethylacetate, vinyl valerate, vinyl caproate, vinyl chloroacetate, vinyl dichloroacetate, vinyl methoxyacetate, vinyl butoxyacetate, vinyl acetoacetate, vinyl lactate, vinyl xcex2-phenylbutyrate or vinyl cyclohexylcarboxylate; a dialkyl itaconate, for example, dimethyl itaconate, diethyl itaconate or dibutyl itaconate; a monoalkyl or dialkyl fumarate, for example, dibutyl fumalate; and others, for example, crotonic acid, itaconic acid, maleic anhydride, maleimide, acrylonitrile, methacrylonitrile or maleonitrile.
In addition, any addition-polymerizable unsaturated compounds copolymerizable with monomers corresponding to the repeating structural units described above may be employed.
A molar ratio of each repeating structural unit in the acid-decomposable resin of component (B) can be appropriately determined taking the adjustment of many factors including dry etching resistance of resist, standard developing solution aptitude, adhesion to substrate, resist profile, and other characteristics ordinarily required for resist, for example, resolution, heat resistance and sensitivity into consideration.
Preferred embodiments of the acid-decomposable resin of component (B) according to the present invention include (1) resin (side chain type) containing a repeating unit having a partial structure including an alicyclic hydrocarbon represented by formula (pI), (pII), (pIII), (pIV), (pV) or (pVI), and (2) resin (main chain type) containing a repeating unit represented by formula (II).
The resin of (2) includes (3) resin (hybrid type) containing a repeating unit represented by formula (II), a maleic anhydride derivative and a (meth)acrylate structure.
A content of the repeating structural unit having a partial structure including an alicyclic hydrocarbon represented by formula (pI), (pII), (pIII), (pIV), (pV) or (pVI) is preferably from 30 to 70% by mole, more preferably from 35 to 65% by mole, and still more preferably from 40 to 60% by mole, based on the total repeating structural units in the acid-decomposable resin.
A content of the repeating structural unit represented by formula (II) is preferably from 10 to 60% by mole, more preferably from 15 to 55% by mole, and still more preferably from 20 to 50% by mole, based on the total repeating structural units in the acid-decomposable resin.
A content of the repeating structural unit corresponding to the additional copolymer component described above can be appropriately determined depending on the desired performance of resist. In general, the content is preferably 99% by mole or less, more preferably 90% by mole or less, still more preferably 80% by mole or less, and most preferably 50% by mole or less, to the sum total of the repeating structural unit having a partial structure including an alicyclic hydrocarbon represented by formula (pI), (pII), (pIII), (pIV), (pV) or (pVI) and the repeating structural unit represented by formula (II).
When the photosensitive composition of the present invention is used for ArF exposure, it is preferred that the acid-decomposable resin does not contain an aromatic group in order to ensure transparency of the ArF beam.
The acid-decomposable resin for use in the present invention can be synthesized according to conventional methods, for example, radical polymerization. For instance, in ordinary synthesis methods, monomers are put into a reaction vessel at once or separately during the reaction, dissolved in a reaction solvent, for example, an ether, e.g., tetrahydrofuran, 1,4-dioxane or diisopropyl ether, a ketone, e.g., methyl ethyl ketone or methyl isobutyl ketone, an ester, e.g., ethyl acetate, or a solvent dissolving the composition of the present invention, e.g., propylene glycol monomethyl ether acetate, if desired, to form a uniform solution, and under inert gas atmosphere, for example, nitrogen or argon, polymerization is initiated using a commercially available radical initiator (e.g., an azo initiator or a peroxide) while heating, if desired. The initiator is further added or separately added, if desired. After the completion of the reaction, the reaction mixture is poured into a solvent to correct the resulting powder or solid, thereby obtaining the polymer. The concentration of reaction is ordinarily not less than 20% by weight, preferably not less than 30% by weight, and more preferably not less than 40% by weight. The reaction temperature is ordinarily from 10 to 150xc2x0 C., preferably from 30 to 120xc2x0 C., and more preferably from 50 to 100xc2x0 C.
A weight average molecular weight of the resin of component (5) for use in the present invention is preferably form 1,000 to 200,000 measured by a GPC method and calculated in terms of polystyrene. It is not preferred that the weight average molecular weight of the resin is less than 1,000, since the degradation of heat resistance and dry etching resistance may occur. On the other hand, when the weight average molecular weight of the resin is more than 200,000, undesirable results, for example, the degradation of developing property and film-forming property due to severe increase in viscosity may occur.
A content of the resin of component (B) according to the present invention in the positive photoresist composition of the present invention is preferably from 40 to 99.99% by weight, and more preferably from 50 to 99.97% by weight, based on the total solid content of the photosensitive composition.
 less than (C) Basic compound greater than 
It is preferred that the positive photosensitive composition of the present invention contains a basic compound of component (C) for restraining fluctuations in performances occurred with the passage of time from exposure to heating.
The basic compound preferably has a structure represented by any one of formulae (A) to (E) shown below. 
In the above formula, R250, R251 and R252, which may be the same or different, each independently represent a hydrogen atom, an alkyl group having from 1 to 6 carbon atoms, an aminoalkyl group having from 1 to 6 carbon atoms, a hydroxyalkyl group having from 1 to 6 carbon atoms or a substituted or unsubstituted aryl group having from 6 to 20 carbon atoms, or R250 and R251 may be combined with each other to form a ring, 
In the above formulae, R253, R254, R255 and R256, which may be the same or different, each independently represent an alkyl group having from 1 to 6 carbon atoms.
Preferred examples of the basic compound include substituted or unsubstituted guanidines, substituted or unsubstituted aminopyridines, substituted or unsubstituted aminoalkylpyridines, substituted or unsubstituted aminopyrrolidines, substituted or unsubstituted indazoles, substituted or unsubstituted pyrazoles, substituted or unsubstituted pyrazines, substituted or unsubstituted pyrimidines, substituted or unsubstituted purines, substituted or unsubstituted imidazolines, substituted or unsubstituted pyrazolines, substituted or unsubstituted piperazines, substituted or unsubstituted aminomorpholines, substituted or unsubstituted aminoalkylmorpholines, mono-, di- or trialkylamines, substituted or unsubstituted anilines, substituted or unsubstituted piperidines and mono- or diethanolamine. Preferred examples of the substituent include an amino group, an aminoalkyl group, an alkylamino group, an aminoaryl group, an arylamino group, an alkyl group, an alkoxy group, an acyl group, an acyloxy group, an aryl group, an aryloxy group, a nitro group, a hydroxy group and a cyano group.
Preferred specific examples of the basic compound include guanidine, 1,1-dimethylguanidine, 1,1,3,3-tetramethylguanidine, 2-aminopyridine, 3-aminopyridine, 4-aminopyridine, 2-dimethylaminopyridine, 4-dimethylaminopyridine, 2-diethylaminopyridine, 2-(aminomethyl)pyridine, 2-amino-3-methylpyridine, 2-amino-4-methylpyridine, 2-amino-5-methylpyridine, 2-amino-6-methylpyridine, 3-aminoethylpyridine, 4-aminoethylpyridine, 3-aminopyrrolidine, piperazine, N-(2-aminoethyl)piperazine, N-(2-aminoethyl)piperidine, 4-amino-2,2,6,6-tetramethylpiperidine, 4-piperidinopiperidine, 2-iminopiperidine, 1-(2-aminoethyl)pyrrolidine, pyrazole, 3-amino-5-methylpyrazole, 5-amino-3-methyl-1-p-tolylpyrazole, pyrazine, 2-(aminomethyl)-5-methylpyrazine, pyrimidine, 2,4-diaminopyrimidine, 4,6-dihydroxypyrimidine, 2-pyrazoline, 3-pyrazoline, N-aminomorpholine, N-(2-aminoethyl)morpholine, 1,5-diazabicyclo[4.3.0]non-5-ene, 1,8-diazabicyclo[5.4.0]undec-7-ene, 2,4,5-triphenylimidazole, tri(n-butyl)amine, tri(n-octyl)amine, N-phenyldiethanolamine, N-hydroxvethylpiperidine, 2,6-diisopropylaniline and N-cyclohexyl-Nxe2x80x2-morpholinoethylthiourea. However, the basic compounds for use in the present invention are not limited thereto.
More preferred compounds include substituted or unsubstituted guanidines, substituted or unsubstituted aminopyrrolidines, substituted or unsubstituted pyrazoles, substituted or unsubstituted pyrazolines, substituted or unsubstituted piperazines, substituted or unsubstituted aminomorpholines, substituted or unsubstituted aminoalkylmorpholines and substituted or unsubstituted piperidines. Compounds having an imidazole structure, a diazabicyclo structure, an onium hydroxide structure, an onium carboxylate structure or a trialkylamine structure are also preferred.
The compound having an imidazole structure includes imidazole, 2,4,5-triphenylimidazole and benzimidazole. The compound having a diazabicyclo structure includes 1,4-diazabicyclo[2.2.2]octane, 1,5-diazabicyclo [4.3.0]non-5-ene and 1,8-diazabicyclo [5.4.0]undec-7-ene. The compound having an onium hydroxide structure includes a triarylsulfonium hydroxide, phenacyl sulfonium hydroxide and a 2-oxoalkyl group-containing sulfoniura hydroxide, e.g., triphenylsulfonium hydroxide, tris (t-butylphenyl) sulfonium hydroxide, bis(tert-butylphenyl) iodonium hydroxide, phenacyl thiopheniurn hydroxide or 2-oxopropylthiophenium hydroxide. The compound having an onium carboxylate structure includes a compound wherein an anion portion of the compound having an onium hydroxide structure is replaced by a carboxylate, e.g., acetate, adamantane-1-carboxylate or a perfluoroalkyl carboxylate. The compound having a trialkylamine structure includes an unsubstituted alkylamine, e.g., triethylamine, tributylamine, trioctylamine or dicyclohexylamine, and an alkylamine substituted with a hydroxy group, e.g., triethanolamine or N-hydroxyethylpiperidine.
The basic compound of component (C) may be used individually or as a mixture of two or more thereof. The amount of basic compound of component (C) used is ordinarily from 0.001 to 10% by weight, and preferably from 0.01 to 5% by weight, based on the solid content of the positive photosensitive composition. When the amount is less than 0.001% by weight, an effect of the addition of basic compound is not obtained. When the amount exceeds 10% by weight, on the other hand, the sensitivity tends to decrease or the developability tends to degrade in the unexposed area.
 less than (D) Fluorine-Base and/or Silicon-base Surface Active Agent greater than 
It is preferred that the positive photosensitive composition of the present invention contains one or more of fluorine-base and/or silicon-base surface active agent (a fluorine atom-containing surface active agent, a silicon atom-containing surface active agent and a surface active agent containing both a fluorine atom and a silicon atom).
By the addition of the surface active agent of component (D), the positive photosensitive composition of the present invention can provide, at high sensitivity and good resolution, resist patterns having good adhesion and less defect in development, when an exposure light source of 250 nm or less, especially 220 nm or less is used.
Specific examples of the surface active agent of component (D) include those as described in JP-A-62-36663, JP-A-61-226746, JP-A-61-226745, JP-A-62-170950, JP-A-63-34540, JP-A-7-230165, JP-A-8-62834, JF-A-9-54432, JP-A-9-5988 and U.S. Pat. Nos. 5,405,720, 5,360,692, 5,529,881, 5,296,330, 5,436,098, 5,576,143, 5,294,511 and 5,824,451. Commercially available surface active agents described below may also be used as they are.
Examples of the commercially available surface active agent used include fluorine-base or silicon-base surface active agents, e.g., Eftop EF301 and EF303 (manufactured by Shin-Akita Kasei Co., Ltd.), Florad FC430 and FC431 (manufactured by Sumitomo 3M Ltd.), Megafac F171, F173, F176, F189 and R08 (manufactured by Dainippon Ink and Chemicals, Inc.), Surflon S-382, SC101, 102, 103, 104, 105 and 106 (manufactured by Asahi Glass Co., Ltd.) and Troysol S-366 (manufactured by Troy Chemical Corp.). A polysiloxane polymer KP-341 (manufactured by Shin-Etsu Chemical Co., Ltd.) is also used as a silicon-base surface active agent.
The amount of surface active agent used is preferably from 0.0001 to 2% by weight, and more preferably from 0.001 to 1% by weight, based on the total amount of the positive photosensitive composition (excluding a solvent).
 less than (E) Organic Solvent greater than 
The positive photosensitive composition of the present invention is used by dissolving the above-described components in the desired organic solvent.
Examples of the organic solvent used include ethylene dichloride, cyclohexanone, cyclopentanone, 2-heptanone, xcex3-butyrolactone, methyl ethyl ketone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, 2-methoxyethyl acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, toluene, ethyl acetate, methyl lactate, ethyl lactate, methyl methoxypropionate, ethyl ethoxypropionate, methyl pyruvate, ethyl pyruvate, propyl pyruvate, N,N-dimethylformamide, dimethylsulfoxide, N-methylpyrrolidone and tetrahydrofuran.
In the present invention, it is preferred to use, as an organic solvent, a mixture of a solvent containing a hydroxy group and a solvent free from a hydroxy group. This makes it possible to restrain the generation of particles during storage of the resist solution.
Examples of the hydroxy group-containing solvent include ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol, propylene glycol monomethyl ether, propylene glycol monoethyl ether and ethyl lactate. Of these solvents, propylene glycol monomethyl ether and ethyl lactate are particularly preferred.
Examples of the solvent free from a hydroxy group include propylene glycol monomethyl ether acetate, ethyl ethoxypropionate, 2-heptanone, xcex3-butyrolactone, cyclohexanone, butyl acetate, N-methylpyrrolidone, N,N-dimethylacetamide and dimethylsulfoxide. Of these solvents, propylene glycol monomethyl ether acetate, ethyl ethoxypropionate, 2-heptanone, xcex3-butyrolactone, cyclohexanone and butyl acetate are particularly preferred, and propylene glycol monomethyl ether acetate, ethyl ethoxypropionate and 2-heptanone are most preferred.
A mixing ratio (by weight) of the hydroxy group-containing solvent to the solvent free from a hydroxy group ranges from 1/99 to 99/1, preferably from 10/90 to 90/10, and more preferably from 20/80 to 60/40. A mixed solvent containing not less than 50% by weight of the solvent free from a hydroxy group is also particularly preferred in view of uniform coating.
 less than (F) Acid Decomposable Dissolution Inhibiting Compound greater than 
It is preferred that the positive photosensitive composition of the present invention contains a dissolution inhibiting low molecular weight compound of component (F) (hereinafter also referred to as an xe2x80x9cacid decomposable dissolution inhibiting compoundxe2x80x9d) having a group capable of being decomposed by the action of an acid to increase solubility in an alkali developing solution and having a molecular weight of not more than 3,000.
In order to prevent deterioration in transmittance at 220 nm or less, an alicyclic or aliphatic compound having an acid decomposable group, for example, a cholic acid derivative having an acid decomposable group as described in Proceeding of SPIE, 2724, 355(1966) is preferred as the acid decomposable dissolution inhibiting compound of component (F). Examples of the acid decomposable group and alicyclic structure are similar to those described regarding the acid decomposable resin of component (B) above.
The amount of acid decomposable dissolution inhibiting compound of component (F) used is preferably from 3 to 50% by weight, and more preferably 5 to 40% by weight, based on the solid content of the total positive photosensitive composition.
Specific examples of the acid decomposable dissolution inhibiting compound of component (F) are set forth below, but the present invention should not be construed as being limited thereto. 
 less than (G) Alkali-soluble Resin greater than 
The positive photosensitive composition of the present invention may contain a resin of component (G), which does not contain an acid-decomposable group, insoluble in water but soluble in an alkali developing solution. By the addition of such a resin, the sensitivity of the photosensitive composition can be improved.
In the present invention, a novolac resin having a molecular weight of from about 1,000 to about 20,000 and a polyhydroxystyrene derivative having a molecular weight of from about 3,000 to about 50,000 are used as such a resin. Since these resins have a large absorption of light of 250 nm or less, they are preferably used after being subjected to partial hydrogenation or in an amount not larger than 30% by weight based on the total amount of resin.
Resins having a carboxy group as an alkali-solubilizing group are also used. The carboxy group-containing resin preferably has a monocyclic or polycyclic alicyclic hydrocarbon group for improving dry etching resistance. Specific examples of such a resin include a methacrylic ester/(meth)acrylic acid copolymer having an alicyclic hydrocarbon structure which does not exhibit acid decomposability and a (meth)acrylic ester resin containing an alicyclic hydrocarbon group having a carboxy group at the terminal thereof.
 less than Other Additives greater than 
Into the positive photosensitive composition of the present invention, a dye, a plasticizer, a surface active agent other than the surface active agent of component (D), a photosensitizer and a compound for promoting dissolution in a developing solution may be incorporated.
The dissolution promoting compound in a developing solution for use in the present invention is a low molecular weight compound having a molecular weight of not more than 1,000 and having at least two phenolic hydroxy groups or at least one carboxy group. In case of containing a carboxy group, an alicyclic or aliphatic compound is preferred because of the same reason as described above.
The amount of dissolution promoting compound used is preferably from 2 to 50% by weight, and more preferably from 5 to 30% by weight, based on the resin capable of being decomposed by the action of an acid to increase a solubility rate in an alkali developing solution of component (B) . The amount exceeding 50% by weight is not preferred, because another problem of the increase in development residue or the deformation of patterns at development may occur.
Such a phenolic compound having a molecular weight of not more than 1,000 can be easily synthesized by one skilled in the art with reference to methods as described, for example, in JP-A-4-122938, JP-A-2-28531, U.S. Pat. No. 4,916,210 and European Patent 219,294.
Specific examples of the carboxy group-containing alicyclic or aliphatic compound include a carboxylic acid derivative having a steroid structure, e.g., cholic acid, deoxycholic acid or lithocholic acid, an adamantanecarboxylic acid derivative, adamantanedicarboxylic acid, cyclohexanecarboxylic acid and cyclohexanedicarboxylic acid, but the present invention should not be construed as being limited thereto.
To the photosensitive composition of the present invention, a surface active agent other than the fluorine-base and/or silicon-base surface active agent of component (D) may be added. Specific examples of such surface active agent include a nonionic surface active agent, for example, a polyoxyethylene alkyl ether, e.g., polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene cetyl ether or polyoxyethylene oleyl ether, a polyoxyethylene alkyl aryl ether, e.g., polyoxyethylene octyl phenol ether or polyoxyethylene nonyl phenol ether, a polyoxyethylene/polyoxypropylene block copolymer, a sorbitan fatty acid ester, e.g., sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan monooleate, sorbitan trioleate or sorbitan tristearate, and a polyoxyethylene sorbitan fatty acid ester, e.g., polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan trioleate or polyoxyethylene sorbitan tristearate.
The surface active agents may be used individually or in combination of two or more thereof.
 less than Method for Use greater than 
The positive photosensitive composition of the present invention is applied onto a desired substrate after dissolving the above components in a desired organic solvent, preferably in the mixed solvent as described above.
Specifically, the photosensitive composition is applied to a substrate (e.g., silicon/silicon dioxide coating) as used for the production of a precision integrated circuit element by appropriate coating means, for example, a spinner or a coater.
After the application, the resulting photosensitive layer is exposed to light through a desired mask, followed by baking and development. Thus, good resist patterns are obtained. As light for the exposure, a far ultraviolet ray having preferably a wavelength of 250 nm or shorter, more preferably 220 nm or shorter is used. Specific examples thereof include a KrF excimer laser beam (248 nm)i an ArF excimer laser beam (193 nm), an F2 excimer laser beam (157 nm), an X-ray and an electron beam. The ArF excimer laser beam (193 nm) is particularly preferred.
In the development step, a developing solution as described below is used. The developing solution for the positive photosensitive composition of the present invention includes an aqueous alkaline solution containing, for example, an inorganic alkali, e.g., sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate or aqueous ammonia, a primary amine, e.g., ethylamine or n-propylamine., a secondary amine, e.g., diethylamine or di-n-butylamine, a tertiary amine, e.g., triethylamine or methyldiethylamine, an alcohol amine, e.g., dimethylethanolamine or triethanolamine, a quaternary ammonium salt, e.g., tetramethylammonium hydroxide or tetraethylammonium hydroxide, and a cyclic amine, e.g., pyrrole or piperidine.
A developing solution prepared by adding an appropriate amount of an alcohol or a surface active agent to the aqueous alkaline solution is also used,
The present invention is described in more detail with reference to the following examples, but the present invention should not be construed as being limited thereto.